Blackmail is a very serious crime. It is dangerous not only for the blackmailed person, but also for the whole society, because it often motivates the blackmailed person to commit other crimes:
In general, the danger of blackmail becomes higher if the rate of detection is small, moreover if
All these points are valid for the AOC laws. That means, the danger of blackmail with violations of AOC laws is very high.
Remark also that in every pedophile relation there is a person which can blackmail the "perpetrator" because he/she knows about his crime and can report about it without the danger of persecution for own participation - the minor.
Considering these facts, it seems even strange that blackmail is not much more common in such relations. Usually they are connected with blackmail by prostitutes or by the parents if they disclose the relation. The best example was the Michael Jackson case.
As an example, Ziegler (in German) mentions two cases of pedophile members of the Bundestag. In one case, an attempt (in disguise) to blackmail him to change his party was described.